1. Field of the Invention
The present invention relates to a tear production measuring sheet which is used to measure the tear production of a patient to diagnose a disease or any other abnormality of the eye on the basis of the volume of tear secretion within a unit time.
2. Prior Art
Among measuring strips used for the above-described purpose, Shirmer test strips have hitherto been known. These strips are made of filter paper, and they each have a width of about 5 mm and a length of about 42 mm. Each strip has a semi-circular tip, and a triangular notch formed on one side of the strip at a location of about 5 mm from the tip. In use, the semi-circular tip portion is bent at the notch, and it is then placed inside the lower eye-lid of a patient. Tear secretion infiltrates into the measuring strip and transmits therein. The amount of tear secretion is determined by visually observing the extent to which the filter paper forming the strip is wetted within a unit time.
For instance, if the unit time is five minutes, a length of the moistened area ranging from 10 to 30 mm (usually 15 mm or thereabouts) is regarded as a normal value. The range of normal values lowers with an increase in the age of patients, and, when the patient is above sixty, the amount of secretion can be considerably small. Lengths below 5 mm are, however, regarded as abnormal values.